The objectives of the proposed studies are to investigate the relationship between immune responsiveness and leukemogenesis in congenic strains of mice. One portion of study will be directed at evaluating the immune responsiveness of HRS/J hr/hr, hr/+, ad +/+ mice. These lines, which are congenic at the hairless locus, have significantly different leukemia incidences which are paralleled by altered general immune responsibeness. This study will evaluate their immune responsiveness to tumor-and murine leukemia virus-antigens and relate these specific responses to rates of leukemogenesis. Also, three strains in which spontaneous nutations to hairlessness were recently found will be evaluated to determine the effect of the presence of the hairless gene on different genetic backgrounds. Experiments are described which will evaluate the leukemia incidence and general immune responsiveness of the new mutants and their respective "wild" types. Similar studies are planned using the congenic resistant strains AKR.L-H-2b.1 and L.AKR-H-2k. The AKR.1-H-1b/1 line has an AKR/J background and is congenic for the H-2b genotype derived from strain c57L/J. These mice have been shown in our laboratory to have delayed and reduced leukemia incidence with respect to AKR/J and preliminary evidence indicates that they also have an latered immune responsiveness. This study is designed to confirm and expand upon these findings. Also, the L.AKR-H-2k line, which has a C57L/J background and is congenic for the H-2k genotype derived from AKR/J will be evaluated to determine its leukemia incidences and overall immune responsiveness. Thus, I plan to examine the relationship between immune responsiveness and leukemogenesis using several congenic mouse strains which are uniquely suited to this type of study. I hope information gained opens the door to future studies in which the immune system can be manipulated in a manner beneficial to the tumor-bearing host.